1. Field of the Invention
The present invention relates to a differential scanning calorimeter, to which a cooling head to be cooled by an external cooling device is detachably connected.
2. Description of the Related Art
The differential scanning calorimeter is a thermal analysis device which changes temperatures of a measuring sample and a reference material stored in a heat sink at a constant speed, to thereby measure a difference in heat flow flowing through the measuring sample and the reference material. The differential scanning calorimeter includes a heater for heating the heat sink and a cooling mechanism for cooling the heat sink. To the cooling mechanism, a gas cooling device (JP 07-122619 B) or an electric cooling device is connected from the outside, to thereby perform cooling. The gas cooling device uses gas obtained by vaporizing liquefied nitrogen or the like, and the electric cooling device uses a coolant cooled by a compressor.
Further, the following differential scanning calorimeter is disclosed as a thermal analysis device (JP 2006-58047 A): a differential scanning calorimeter in which a cooling mechanism itself has an insertion hole formed therein, into which a cooling head is inserted and which allows an external electric cooling device to be detachably connected to the cooling mechanism, and a discharge flow path continuous with the insertion hole is provided so as to enable gas cooling of the cooling mechanism itself.
Further, there is disclosed a scanning calorimeter in which a cooling flange provided with a cylindrical disk is connected through a thermal resistor to the lower portion of the heat sink (JP 2002-310965 A (FIG. 1 and paragraph 0045)).
However, the gas cooling device involves complicated supplement of the coolant and high running cost, while the electric cooling device is allowed to be used only in a limited temperature range. Therefore, when only one of the gas cooling device and the electric cooling device is allowed to be used for cooling, measurement by the differential scanning calorimeter is restricted.
Further, in the case of the technology described in JP 2002-310965 A, the external cooling device is mounted on a top surface 12 of a cooling flange (cooling block) 10. Therefore, the cooling head of the cooling device is adjacent to a thermal resistor 9 on the cooling flange 10 so as to directly face thereto, and unignorable heat inflow through an air layer occurs between the cooling head and the thermal resistor 9. This occurs because the cooling head and the thermal resistor 9 have a temperature difference of 100° C. or higher therebetween. In this case, thermal effects by radiation, convection, and the like occur between the cooling head and the thermal resistor 9, which leads to imbalance and destabilization of the heat conduction to the heat sink. Meanwhile, when the cooling head is separated away from the thermal resistor 9 to be brought into contact with the cooling flange 10, thermal resistance occurs in the cooling flange 10. As a result, temperature distribution of the cooling flange 10 becomes wider, and cooling efficiency is reduced.
On the other hand, in the case of the technology described in JP 2006-58047 A, the cooling head is completely housed in the cooling mechanism (cooling block), and hence the problem of heat inflow between the cooling head and the thermal resistor does not occur. However, the cylindrical cooling head is inserted into the cooling block at a deviated position, and hence there is a risk that the cooling block is not uniformly cooled. Regarding this risk, the technology described in JP 2006-58047 A has room for improvement.